I. Field of the Invention
The present disclosure relates generally to telecommunications, and more particularly, to concepts for locating a wireless local area network associated with a wireless wide area network.
II. Background
Wireless networks, such as those supporting GSM, WCDMA, cdma2000 and TDMA, commonly provide wireless coverage over a large geographic area—for example, a city, metropolitan area, a state or county or sometimes a whole country. Such networks are sometimes referred to as WWANs (Wireless Wide Area Networks). Recently, smaller wireless networks known as WLANs (Wireless Local Area Networks) have been standardized, for example by the IEEE 802.11 committee, and deployed to cover small areas with a geographic coverage ranging from a few tens of meters to a few hundred meters. To enable wider coverage using these networks, it is common to deploy many such networks in different adjacent areas. In some cases, the ensemble of such multiple WLANs may be considered as a small WWAN in its own right with each “cell” of the WWAN being supported by a single WLAN. Such WLANs or WLAN ensembles may be owned and operated by independent operators or by the same operators who own and run WWANs or by individual subscribers (e.g., home or office WLANs).
For WWAN operators who own WLANs or have a business arrangement with WLAN operators (e.g., including WWAN subscribers who own WLANs), there may be an advantage in allowing or assisting wireless terminals to access such WLANs as a means of extending coverage (e.g., into areas served by WLANs but not by WWANs) and/or increasing capacity in the case that existing WWAN resources (e.g., available spectrum) are insufficient to serve all subscribers. For example, extension of coverage may be an advantage in areas harder to reach by WWANs (e.g., within shopping malls, inside homes and offices) while increasing capacity may be an advantage in the most heavily used areas (e.g., urban environments), during peak usage times and to reduce WWAN resource utilization.
In the event that wireless terminals are allowed or may be required to use certain WLANs when available, it may become necessary to make the terminal aware that a particular WLAN or set of WLANs is or are available at any particular location in which the terminal happens to be. This could be supported by having the wireless terminal perform periodic searches for available WLANs and then, if a suitable WLAN is found and its signal strength is deemed adequate, have the terminal transfer its service to the WLAN (e.g., via registration on the WLAN and handover of any ongoing services, such as a call, that the terminal may be engaged in). The problem with this simple approach is that any frequent scanning for available WLANs may consume excessive resources in the terminal (e.g., battery) as well as interfere with ongoing services. Furthermore, if maintaining ongoing services has higher priority, it may not always be possible to adequately scan for available WLANs. It could thus be an advantage to have other methods of finding available and suitable WLANs that do not involve excessive resource utilization in a terminal or conflict with the support of existing services.
One such method has been defined to support WLAN access from terminals using CDMA, for example cdma2000, WWANs. This method makes use of the fact that transmissions from CDMA base stations can be synchronized. Specifically, the concept makes use of synchronized timing in CDMA base stations which enables a wireless terminal to measure pilot phases from nearby base stations and use these to indicate its approximate geographic location. By recording pilot phases associated with the availability of a particular WLAN, the handset can, at a later time, determine the proximity of the same WLAN when it measures the same pilot phases that it had recorded previously. This enables a wireless terminal to perform handover to the WLAN (once it is detected) and help alleviate congestion on a normal WWAN or extend WWAN coverage.
However, the above concept does not address asynchronous networks like GSM and WCDMA because information equivalent to CDMA pilot phases is not supported in these networks in a form that can be directly used. Accordingly, there exists a need for new technology that may be used to help locate WLANs in association with both asynchronous and synchronous WWANs.